Transmission line



TRANSMISSION LINE Filed July 21, 195e 2 sheets-sheet 1 TRA NSM] TTER mwf 20 INVENTOR LUDWIG A. BATTERMANN BY y ATTO R N EY April 4, 1939.

L. A. BATTERMANN TRANSMISSION LINE Filed July 2l, 1936 2 Sheets-Sheet 2INVENTOR LUDWIG BATTERMAN N ATTO R N EY Patented Apr. 4, 1939 UNITEDSTATES PATENT OFFICE TRANSMISSION LINE tion of Delaware Application July21, 1936, Serial No. 91,641

10 Claims.

This invention relates to an improved trans mission line of the coaxialtype of conductor and is particularly adapted to the method and means ofjoining the conductor sections together to form a low resistance jointhaving substantially no high frequency wave reflection even when usedwith ultra-short wave circuits.

An object of this invention is to simplify and improve the method ofjoining the several sections of concentric conductors.

Another object of this invention is to provide a transmission line whichmay be taken apart at wili and reconnected again so as to maintain a lowresistance joint with substantially no high frequency losses.

Still another object of this invention is to accurately maintain theinside diameter of the outer conductor and the outside diameter of theinner conductor continuously throughout the entire length of theconcentric conductor, that is, from the point where the concentric lineis conn nected to the transmitter to the point where the line isconnected to the antenna.

A feature of this invention is the improved internal and external unionswhich allow quick repairs or changes in the transmission lines to bemade and at the same time maintain substantially no losses at theultra-high frequencies.

In the prior art, joints in the outer and inner conductors of a coaxialline were made by soldering, brazing, or by lap or split joints heldtogether by means of screws or bolts. By the first mentioned solderingor brazing method, the conductor could not be conveniently taken apartand irequently there were places in which the inner conductor could notbe conveniently reached in order to satisfactorily solder the varioussections to gether. In the second mentioned method, the joints could betaken apart conveniently but they did not present a perfect continuityof low loss electrical path. This present invention makes possible animproved joint which can be immediately disassembled and whenreassembled will present a perfectly smooth surface and a'perfectcontinuity of low loss electrical path even when used in an ultra-highfrequency circuit.

This invention will best be understood by referring to the accompanyingdrawings, in which:

Fig. 1 is the general arrangement of the transmission line;

Fig. 2 is a view of the improved coupling of a transmission line shownpartly in section and partly in elevation;

Fig. 3 is an end view of Fig. 2;

Fig. 4 is a detail of the improved union for joining the innerconductor, shown partly in section and partly in elevation;

Fig. 5 is an end view of Fig. 4;

Fig. 6 is a detail partly in section and partly in elevation oi theinner conductor of a transmission 5 line having substantially heavymetallic walls; while Fig. 'l is a detail partly in elevation and partlyin section of an inner conductor in which the device of this inventionis used to join two conduo l0 tors of unequal diameter.

Referring now in detail to Fig. l, the coaxial line comprises an outerconductor i and an inner conductor 2 which are concentrlcally spacedapart from each other by any suitable insulation means, l5 such as astar-like or spider arrangement 3. One end of the conductors is joinedto a transmitter d and the other end is connected to an antenna 5.Certain sections of the inner and outer conductors are joined togetherat points 6 and l', the joints of which are to be described in furtherdetail by Figs. 2 and 3.

In Figs. 2 and 3, a section of the outer conductor I is provided with ashouldered end 8 which may form a part of the same material as conductorI or may be a separate collar as indicated by dotted lines and joined byany suitable means, such as soldering, brazing or welding at a point9.'I'he other section of the outer conductor I is likewise provided with acollar I0 which is threaded preferably with a right-hand thread I I. Theend faces of members 8 and I0 are cut on a slight angle so that themaximum length of the conductor occurs at points I2 and I3 each of whichis the periphery determined by the inner diameter of the outerconductor, forming a shoulder bearing against the inner end of the outerconductor. A split spacing member I4 radially split at I4' is interposedbetween the end faces of members 8 and II), and this member likewise hasits end faces chamfered off at a slight angle so as to provide a maximumlength at the periphery determined by the inner diameter of the outerconductor. Members 8, I4 and I0 are joined together by means oi anexternal cap-like coupling member I5. As indicated by dotted lines, theinner conductor 2 is provided with internal bushing members IB and I'Iwhich are fastened inte gral to the ends of tubes 2 by any suitablemeans such as soldering, welding or brazing, or thread a ing. Bushingmember I6 is preferably threaded with an internal left-hand thread I8and bushing member I 'I is threaded with a. right-hand thread I9. Aninternal plug or stub 20 joins together members I6 and I1. Member 20 isprovided with an aperture 2l in which a suitable rod-like wrench isplaced in order that the sections may be securely joined together. Acollar or spacing member 22 maintains members IB and i1 in proper spacedrelationship and is provided with slotted apertures 2l'. The ends ofmember 22 are slightly chamfered so that the maximum length occurs atthe periphery of the outer diameter. Likewise, members I6 and i1 arecorrespondingly chamfered so that the points of contact of members il,i1 and 22 occur only at the point of the outside diameter of the innerconductor 2. It is to be noted that a feature of this construction isthat the thrust exerted by the nut member Il upon collars I and i0 istaken by the shoulders on the collars B and I0. This important featurealso prevents the tightening of the nut Il from stripping the collars 8and I0 from the ends of the outer conductor.

Figs. 4 and 5 show a detail of a single internal coupling member whichis provided with ends having a left-hand thread 23 and a right-handthread 24. The ends of the threaded portions 23 and 24 are rounded overat points 25 and 23. As mentioned, the point of contact of the outerperiphery is arranged so that its maximum length or point of contact isat the outer edge at point v29 to make contact with the maximum outsideof inner conductor 20, should it be desired to omit member 22.

In the modification shown by Fig. 6, the inner conductors are threadedto receive member 20, member 22 having its edge chamfered as mentionedabove and the outer diameters of tubes III being likewise chamfered sothat the point of contact is at the outer periphery where members 20 and22 Join.

Fig. 'I shows a larger pipe or inner conductor Il Joined to a smallerpipe 32, members 20 and 22 being identical with that shown in Figs. 2and 3, except that the extreme end of pipe Il is provided with an endplug 22 having a left-hand thread 34 which is oi' the same diameter asthe thread II.

It is, of course, understood that in the case of a joint around thecoaxial conductors of one size and a joint around coaxial conductors ofa dinerent size, as shown in Fig. '7, for the inner conductor, therewill be correspondingly unequal sizes in the outer conductors which willrequire a suitable modincation of the union I5 for the outer conductor.'111e joints of the transmission line may be as numerous as required tofacilitate the fabrication and installation of the radio equipment.Whenever it is desirable to Join a concentric or coaxial transmissionline to the stub coaxial line, vwhich is that portion of thetransmission lines lying within the confines of the transmitter itselfand to which the external part of the transmission line is to beattached or connected, assuming that the transmission line and the stubline are of equal diameter, that is, inner conductor to inner conductorand outer conductor to outer conductor, then the general assembly is asshown diagrammatically in Figs. 2 and 3.

It is, of course, assumed that the transmitter has previously been setin its position and that the transmission line has been built and thatthere is a space between the ends of the inner conductor equal to thelength of the collar 22 and between the outside conductor ends there isa space equal to the length of the split sleeve Il. It is also to beassumed that bushings I6 and I1 have been secured in place and that theunion I5 amasar and its restraining collar l have been secured to oneend say, for example, the stub section of the outside conductor, and thethreaded collar I0 has been secured to the transmission line end of thecoupling. Then, placing the collar 22 on stud 20, the transmission line2 is moved away from the stub line so that stud 2li may be started tothread into the bushings i8 and I1, turning member 20 clockwise lookingfrom its front end toward the rear, by means of a rod-like tool throughthe central aperture 2i. Since the collar 22 is longer than the middlesection of member 20, it will compensate if both threaded ends of member20 do not start to thread at the same turn. After members 2 are securelybound together, the tightening rod should be removed and there will beprovided a smooth continuous outer surface at the joint of the innerconductor which does not offer high resistance or reflection even to ahigh frequency electrical current. To fasten the outer conductorstogether, split sleeve i4 is held in position, the union nut i5 is slidover the outer conductor l and threaded onto the threaded sleeve I0, andis tightened by turning nut i! with a strap wrench. It will be noted byreferring to Fig. 2 of the drawings that there is provided a smoothinner surface at the inside joint of the outer conductor which will notoffer high resistance of reflection. It will be seen that by Joining thesections of coaxial transmission lines together by this invention thatit can be accomplished without the application of any heat at the placeof installation so that any painted surface is not destroyed, nor is anypolished metal discolored.

While only a few modifications of this invention are shown, it is to bedistinctly understood that it is not to be limited to thesemodiiications, except those as are shown in the appended claims.

What is claimed is:

1. A transmission line comprising an outer conductor including aplurality of sections, an inner conductor including a plurality ofsections, insulating members spacing said conductors in concentricrelationship, a chamfered end on each section of said outer and innerconductors, threaded means for joining two sections of both the innerand outer conductors together, securing means interposed between eachconductor comprising an external threaded cap having threads at only oneend thereof, and an internal threaded member having both ends threadedto join the two sections of the inner conductor together.

2. A transmission line comprising an outer conductor including aplurality of sections, an inner conductor including a plurality ofsections, insulating members spacing said conductors in concentricrelationship, a chamfered end on each section of said outer and innerconductors, threaded means for joining two sections of both the innerand outer conductorstogether, clamping means interposed between eachconductor comprising an external threaded cap having threads at only oneend thereof and an internal threaded member having a right hand threadat one end of said member and a left hand thread at the other end ofsaid member for joining the two sections of the inner conductortogether.

3. A transmission line comprising an outer conductor including aplurality of sections, an inner conductor including a plurality ofsections, insulating means for spacing said conductors in concentricrelationship, a spacing member having the same inside diameter as theinside diameter of u said outer conductor, and an external clamping capsurrounding said spacing member, said member and said clamping cap beinginterposed between sections of the outer conductor, an internal threadedmember having a smaller diameter than the outside diameter of said innerconductor for joining two sections of said inner conductor together, andan internal spacing member interposed between the two sections of theinner conductor, said spacing member having an outside diameter equal tothe outside diameter of said inner conductor.

4. A transmission line comprising an outer conductor including aplurality of sections, an inner conductor including a plurality ofsections, insulating means for spacing said conductors in concentricrelationship, a spacing member hav- Aing the same inside diameter as theinside diameter of said outer conductor, and an external clamping capsurrounding said spacing member, said member and said clamping cap beinginterposed between sections oi the outer conductor, an internal threadedmember having a smaller diameter than the outside diameter of said innerconductor for joining two sections of said inner conductor together, andan internal spacing member having an inside diameter oi' such adimension as to be a sliding fit over the central portion of saidinternal threaded member.

5. A transmission line comprising an outer con- -ductor including aplurality oi sections, an inner conductor including a plurality ofsections, insulating members spacing said conductors in concentricrelationship, a chamfered end on each section of said outer and innerconductors, threaded means for `joining two sections of both the innerand outer conductors together including clamping means interposedbetween each conductor comprising a shouldered member located at each ofthe ends of said inner and outer conductors, an external threaded caphaving threads at only one end thereof for joining two sections of saidouter conductor together, and an internal threaded member having a righthand thread at one end and a lett hand thread at the other end forjoining the two sections of the inner conductor together.

6. A transmission line comprising an outer conductor including aplurality of sections, an inner conductor including a plurality ofsections, means for spacing said conductors in concentric relationship,clamping means interposed between each adjacent section of saidconductors comprising a shouldered portion located at ends of eachadjacent section of said inner and outer conductors, the points ofelectrical contact being located and maintained at the inside oi theouter conductor and the outside oi the inner conductor by havingchamfered ends on said sections of both the outer and inner conductors.

7. A transmission line having mechanical and electrical couplingelements comprising an outer conductor including a plurality ofsections, an inner conductor including a plurality of sections, achamfered end on each section of said inner and outer conductors. meansfor insulatingly spacing said conductors in concentric relationship,clamping me'ans interposed between the ends of said conductorscomprising a shouldered bushing having its shouldered portion extendingabove each of the ends of said outer conductor, a second shoulderedbushing having its shouldered portion abutting the ends of each sectionof said inner conductor, a threaded external member clamping saidshouldered bushing for joining two sections of said outer conductortogether, and an internal member clamping said shouldered bush ings forjoining two sections of said inner conductor together,

8. A transmission line comprising an outer conductor including aplurality of sections, an inner conductor including a plurality ofsections, means for spacing said conductors in concentric relationship,a chamfered/end on each section of said outer and inner conductors tomaintain the point of electrical contact at the inside diameter of theouter conductor and the outside diameter of the inner conductor, meansfor Joining two sections oi both the inner and outer conductorstogether, said means comprising an external member interposed betweenthe two sections of the outer conductor and having a larger diameterthan the outside of the outer conductor, and an internal memberinterposed between the two sections of the inner conductor and having asmaller diameter than the outside of the inner conductor.

9. A transmission line comprising an outer conductor including aplurality of sections, an inner conductor including a plurality ofsections, means for spacing said conductors in concentric relationship,a chamfered end on each section of said outer and inner conductors tomaintain the point of electrical contact at the inside diameter of theouter conductor and the outside diameter of the inner conductor, meansfor joining two sections of both the inner and outer conductorstogether, said means comprising an external threaded member interposedbetween the two sections of the outer conductor and having a largerdiameter than the outside of said outer conductor, and an internalthreaded member interposed between the two sections of the internalconductor and having a smaller diameter than the outside diameter of theinner conductor.

10. A transmission `line comprising an outer conductor including aplurality of sections, an innerlconductor including a plurality ofsections, insulating means for spacing said conductors in concentricrelationship, a radially split spacing member having the same insidediameter as the inside diameter of said outer conductor, and an externalclamping cap surrounding said radially split spacing member, saidradially split vspacing member and said clamping cap being interposedbetween sections of the outer conductor, an in ternal threaded memberhaving a smaller diameter than the outside diameter of said innerconductor for joining two sections of said inner conductor together, andan external spacing member having an inside diameter of such a dimensionas to be a sliding nt over the central portion ot said

